1. Field of the Invention
The present invention is directed toward communication related systems, wide area and local area networks, apparatuses and methods as well as computer based digital signal processing mechanisms and methods used therein. More particularly, the invention is directed toward communication systems, methods, and apparatuses that use signals that are modulated using a combination of FSK modulation and QAM submodulation.
2. Discussion of the Background:
It would be advantageous if a remote environmental monitor, a utility meter (e.g., water, gas, or electric), a security system, a mobile data application, or other remote device, hereafter referred to as a “remote endpoint,” could communicate with a base station receiver which in turn would forward the endpoint information (e.g., impurity count, meter read, alarm, or position fix) to some central location. This central location could be part of a wide area network (WAN), or a local area network (LAN).
WAN Applications
Cost to Acquire Remote Endpoint Data
The cost to acquire information from remote endpoints includes (using a remote meter monitoring application as an example) the cost of the meter interface, the meter transmitter (or transceiver), the remote receiver (or transceiver), as well as the forwarding infrastructure, including radio spectrum costs. For example, if the remote receiver has a very limited range such that it can only communicate with one meter, then the cost of that receiver must be fully burdened into the cost to acquire the meter information. Additionally, the cost to install and maintain that remote receiver must be fully burdened as well.
It would therefore be desirable to have a remote receiver (transceiver) communicate with as many endpoints as possible. It would be advantageous if the remote receivers were each able to cover as great a range as possible. Having sufficient range would eliminate costly intermediate tiers of repeaters and/or store-and-forward hand-off devices. It would be advantageous if a radio system that could communicate over many miles were very reliable since the loss of a base station that is responsible for receiving data from thousands or tens of thousands of remote endpoints could be devastating.
Furthermore, it would advantageous if the system were not readily susceptible to jamming. Any source of interference within “view” (i.e., listening range) of a receiver can severely degrade the reliability of the system. Such degradation in reliability translates into a reduced range of the system. A five-block range creates a view area of approximately 0.8 square miles. A 10-mile range creates a view of 314 square miles. Accordingly, an increase in range brings a quadratic increase in the probability of an in-view interference source (the area in a circle is a function of the square of the range).
Conventional approaches for wide area remote monitoring, may be broadly categorized into three groups: short range, long range, and very long range (i.e., satellite).
Short Range Products (One Mile or Less)
Products falling into this category generally have high infrastructure costs associated with them. Large numbers of remote receivers must be bought, installed and maintained. By their nature, short-range devices require either a receiver dedicated to a single endpoint, or intermediate transceivers set up in a cellular or repeater fashion to create multiple tiers of data handoff. Some shorter-range strategies require that a receiver be co-located with a cable box, home computer, modem, or in a drive-by vehicle. These approaches do not yield ubiquitous coverage area and/or are poorly controlled and thus not a reliable alternative.
Long Range Products (One Mile or More)
Conventional long-range communications services for multi-point-to-point monitoring are based on two-way communications. Two-way handshaking is needed to dynamically assign frequency channel usage amongst customers. In the case of voice and two-way messaging, it is a logical requirement (users “talk” and “listen”)
Very Long Range Products (Satellite)
A satellite's greatest advantage, range, is also a weakness. As the range (footprint) increases, the number of endpoints in view increases quadratically, and so does required bandwidth. A competitive satellite system would require approximately 200 MHz of bandwidth to equate to 500 KHz of terrestrial base stations. This will considerably impede satellites from servicing dense applications that require updates every 15 minutes. In addition, present satellite systems are two-way (a requirement for licensed frequency dynamic allocation). This creates a permanent three times or greater cost disadvantage for such systems (present satellite transceivers have at least a 20 times cost disadvantage due to other factors such as very tight ppm budgets). Further, the required update rates would yield unacceptable battery life.
Most of the LAN data communications suppliers and standards (IEEE 802.11, Bluetooth, Swap Home RF, ultrawide bandwidth, etc.) are focused on the high data rate (1-10 million bits per second) market required for PC-to-PC connection.
These higher data rates significantly reduce range and therefore require more closely spaced base stations. This in turn increases hardware and installation cost. This also can increase the requirement for repeaters.